American films could use a lot more audacity, and not merely in the sophomoric zest of the “South Park” comedies or the ambiguous ironies of Todd Solondz’s politically incorrect social satires. It might also be possible to arouse an audience with cool elegance and matter-of-factness about seemingly shocking details. And at the outset, that’s what happens in “Shadowboxer.” First-time director Lee Daniels, who produced the fierce, feverish “Monster’s Ball,” sets up a tempting premise: the quasi-incestuous relationship between two lovers who also happen to be contract killers.

Mr. Daniels underscores the opening scenes with graceful, gliding camera movements and introduces his characters amid impressionistic flashbacks set to the sophisticated heat of Astor Piazzolla’s “Libertango.”

It quickly becomes clear that the differences in age, race, and nationality between Mikey (Cuba Gooding Jr.) and Rose (Helen Mirren) are less significant than the cancer that’s killing her. It’s not killing her too fast, though, despite a horrible wracking cough and Oscar-worthy facial contortions that disrupt long gazes out her luxury loft window to the Philadelphia skyline. She still has time to smoke, drink whiskey, and stoically philosophize as she gives Mikey a bath. The act delivers a potent, intimate charge that might have sustained the film had Mr. Daniels stuck to its emotional core, which resonates as the details of the couple’s relationship are gradually uncovered.The story focuses immediately on Rose’s spiritual awakening, as she second-guesses the history of violence in her life, and decides that the pair’s next job together will be her last.

But the film quickly cuts to sadistic gangster — and fellow hit-man — Clayton (shaggy-dog goofball Stephen Dorff, going the Alec Baldwin route towards B-movie villainy), about to sodomize an unfaithful associate with a broken pool cue. He’s the kind of bad guy who has a zebra grazing in the front yard of his mansion, yet works out of a grimy back alley with a crew of “Sopranos” cast offs. Since Clayton is a figure of pure and casual malevolence, plagued by paranoia, he decides to whack his entire entourage along with his Jersey Girl wife, Vickie (Vanessa Ferlito, of “CSI: New York”), whom he suspects has slept with all his henchmen. Naturally he calls Rose to handle the task. And what happens when Rose stands over Vickie’s bed, silencer in hand, poised to deliver the coup de grace? Why, of course — the intended victim turns out to be nine months pregnant, her water breaks, and the killer’s maternal instincts kick in, delivering a bawling bundle of joy in what must be the shortest labor in the history of childbirth.

This is just one of many surprises in “Shadowboxer,” a film addicted to jarring juxtaposition. Mr. Daniels never manages to reconcile his affection for lyrical — even lushly overblown — interludes with the visceral eruptions of action and even outrageous bits of slapstick that accompany them. He’s got a great eye for talent, and a knack for pushing actors into nervous moments of inspired performance that, again and again, cause viewers to root for his movie and its sheer eccentric bravado. There’s a sharp, funny performance by Joseph Gordon-Levitt as a criminal physician who stitches up survivors of shoot-outs, and tends to brand new moms on the lam (and cohabitates with a crack-addicted nurse named Precious, played by comedienne Mo’Nique, who seems to be auditioning for the next John Waters epic). There’s also a poignant, funkalicious bit by the singer Macy Gray, she of the baby-doll-with-laryngitis voice, who receives too early a visit from Mr. Gooding’s smooth and inventive Angel of Death. And there is, indelibly, the sight of an exposed Mr. Dorff’s dangling condom, back-lit by a blue neon cross when a shoot-out interrupts his vigorous back-door liaison.

There is enough going on here to fill three movies, and two of them might have been good. But just as he oversells the “gotcha!” scenes that punctuate the narrative, Mr. Daniels finally chooses a trite resolution that undersells his ambitions. What begins as something existential and vaguely French in spirit turns into a grimly determined Lifetime Channel version of “Married to the Mob.” That’s not audacious. It’s just predictable.